The gas hole standard of aluminum alloy die casting stipulates the principle of grading and rating method of low porosity of aluminum alloy casts, which is applied to sand casting for aluminum alloy. It fits for the outer surface of the casting and the surface gas hole and pinholes after machining. Gas hole standard can be used in GB1173-86 & GB9438-88 aluminum alloy casting technical conditions, GB10851-89 cast aluminum alloy pinhole.

Features of gas hole and pinhole
1. A gas hole which is located in the casts without extending to the outer part.
(1) Gas hole, pinhole and circular hole with different sizes, single or multiple distributed in the various parts of the casting.
(2) The feature of slag hole is similar to porosity and pinhole, but with slag.

2. The gas hole which is on or near the surface mostly exposed or connected with the outer surface.
(1) Holes on or under the surface: single or multiple holes which are on or near the surface with smooth wall.
(2) Surface pinhole: small holes are on the castings surface, which appear in a larger area.

Specific conditions
1. The non-machined and machined surface of the sand and metal type casting, the following holes are allowed after the cleanliness.
(1) The maximum diameter of a single hole can not exceed 3mm, the depth can not exceed 1/3 of the wall thickness, the installation side can not exceed 1/4 of the wall thickness, symmetric part of the opposite of the same section can not have the same defect.
(2) Groups of holes- the maximum diameter should be less than 2mm, the largest diameter of is not greater than 2mm, the depth should not exceed 1/3 of the wall thickness, and less than 1.5mm.

2. The processing surface of the hydraulic and pneumatic part should pass 3-pinhole as the basis acceptance. Two pinholes should cover over 25% of the acceptance, partially allow 4 pinhole, but less than 25%. When you meet the technology of tightness, sand and metal casts are allowed to pass lower level pinhole acceptance.

3. Threaded hole screw into four pitches without any defects, apart from four pitches, whether it can be allowed to have defects or not, the size and number of the defect should based on the drawing.

4. When there is no special specification for the bubbles inside the casts, the acceptance should be as the following.
(1) The maximum size of a single blister or inclusion should be less than 3mm, the depth should not exceed 1/3 of the wall thickness and 1/4 of the wall thickness on the installation side, the number of the area of 10cmXcm should be less than 3, margin is more than 30mm.
(2) The maximum size of group blisters and inclusions should be less than 1.5mm, the depth can not exceed 1/3 of the wall thickness, the number of the area of 3cm X 3cm should be less than 3, the distance between groups is more than 50mm.
(3) Don't take a single blister or inclusions that are less than 0.5mm into account.
(4) Blister and the distance between the edge of the casting and the edge of inner hole should be more than twice of the maximum size of the inclusion or blister.
(5) The surface of the opposite site of defects we mentioned above are not allowed to have similar defects.